Thanks for the responses.
Yea the tiles used in my example seem a bit simplified with some restrictions (like not having very narrow walls). But if you wanted to have no restrictions and wanted to cover every possibility, then you need to account for potential wall-or-floor on any of the 8 adjacent tiles (otherwise it would not "link" correctly and you'd get artifacts). And since which means 2^8 possibilities. Or maybe my math-fu is failing me? H
The problem becomes more pronounced with more tight environments (i.e. rooms/corridors with lots of turns separated by just one or two walls max). Like here:
Merely "corner in + corner out + wall" wouldn't cut it. I do realize a lot of those are rotated/flipped versions but I am talking about the actual # of tiles required without mirroring/rotating/layering.
Wouldn't mirroring/rotating/layering lead to potential glitches? You can't flip/rotate if unless your walls are symmetrical. And you can't layer some combinations, like side walls that would intersect as that would make them not connect properly.
Hmm I think I will go with the Autotile solution from RPG gamer for now, as it seems to be the most dynamic.